1. Field of the Invention
The present invention relates to the production of novel rare earth oxides, and, more especially, to the production of novel rare earth oxides having large specific surfaces.
In the description which follows, the specific surface is defined as the B.E.T. specific surface determined by the BRUNAUER--EMMETT--TELLER method, described in Journal of the American Chemical Society, 60, 309 (1938).
By the term "rare earths" are intended the metallic elements such as yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutecium.
2. Description of the Prior Art
For numerous applications, such as, for example, in the field of catalysis, it is desirable to employ rare earth oxides having a large specific surface.
The conventional processes for producing rare earth oxides by the calcination of a salt of a rare earth, in the form of a carbonate, a hydroxide or an oxalate, at an elevated temperature, provide rare earth oxides having a relatively small specific surface. Compare S. Bernal et al, Journal of Less-Common Metals, 94, 145-150 (1983), describing rare earth oxides having a specific surface ranging from 15.1 to 40.5 m.sup.2 /g after calcination at 500.degree. C.
In published French Application No. 2,584,701, a neodymium oxide obtained by the calcination of a neodymium hydroxynitrate is described. However, the resulting oxide, while having an increased specific surface relative to the conventional products, has a specific surface ranging from 5 to 30 m.sup.2 /g after calcination at a temperature of from 700.degree. to 900.degree. C.